close the kitchen completely 10 minutes before films.
announce films.
close the curtain and hang a sign which says 'film night, kitchen closed, silence if entering, no laptops, and has the film program' - or something like that.
switch all lights off.
between films, open the kitchen briefly for drinks and cakes/popcorn only.
have a really interesting and innovative program with some strange and amazing short films.

in short, make it a very special event, that people think is amazing.

have the program sorted 6 weeks in advance so that it appears on events posters.
have ur own film posters.

Magda's idea of showing films later was a good one. There is less interference with the normal activities of the cafe and it is arguably easier to concentrate on a film when it is late and you are fed & watered & totally relaxed.

I think both can happily co-exist. For a while Nick Beeson was having an unofficial film night after closing for volunteers and their friends. Apart from being unnessesarily exclusive, it was perfect. It didn't interfere with anything or anyone, and nothing interfered with it.